玄数

negative   负

• Less than zero.
• A quantity, number, angle, velocity, or direction in a sense opposite to another of the same magnitude indicated or understood to be positive.

net weight   净重
Tthe weight of the contents only, excluding the weight of the container or packaging.

nonagon   九边形
A polygon having nine angles and nine sides.

normal   法线；正交的

• A perpendicular line or plane, especially one perpendicular to a tangent line of a curve, or a tangent plane of a surface, at the point of contact.
• The portion of this perpendicular line included between its point of contact with the curve and the x-axis.

normal distribution   正态分布
The usual way in which a particular feature varies among a large number of things or people, represented on a graph by a line that rises to a high symmetrical curve in the middle.

notation   符号
A system of signs or symbols used to represent information, especially in mathematics, science and music.

nought   零
The digit 0; zero: used esp in counting or numbering.

number   数字
A word or symbol that represents an amount or a quantity. A member of any of the following sets of mathematical objects: integers, rational numbers, real numbers, and complex numbers. These sets can be derived from the positive integers through various algebraic and analytic constructions.

number line   数轴
A line that graphically expresses the real numbers as a series of points distributed about a point arbitrarily designated as zero and in which the magnitude of each number is represented by the distance of the corresponding point from zero.

number sense   数感
In mathematics education, number sense can refer to “an intuitive understanding of numbers, their magnitude, relationships, and how they are affected by operations.”[1] Other definitions of number sense emphasize an ability to work outside of the traditionally taught algorithms, e.g., “a well organised conceptual framework of number information that enables a person to understand numbers and number relationships and to solve mathematical problems that are not bound by traditional algorithms”.

number system   数制
Any system of naming or representing numbers, as the decimal system or the binary system.

numeral   数字
A symbol or mark used to represent a number.

numerator   分子
The expression written above the line in a common fraction to indicate the number of parts of the whole. The numerator of the fraction 2/3 is 2.